In a real time video transmission system of a prior art, it is prescribed in a standard that, when a video is to be transmitted, an instantaneous decoding refresh (IDR) picture is inserted and then a predictive picture (P picture) and so forth are inserted. In recent years, it is sometimes tried to reduce a delay by decreasing an encoding buffer amount in accordance with an information amount of the P picture whose information amount is smaller than that of the IDR picture.
Here, a timing at which an IDR picture is inserted is a timing at which the picture order count (POC) value indicates a maximum value. The POC value is a value that counts up every time a video is encoded to generate a P picture. If an IDR picture is inserted, then the POC value is reset to an initial value. According to a prior art, an IDR picture is inserted before the POC value overflows.
FIG. 7 is a view illustrating a timing at which an IDR picture is inserted according to a prior art. As an example, it is assumed that P pictures 10 to 17 are successively inserted and the POC value at a timing at which the P picture 17 is inserted is 999 and then the POC value changes to 1000, which is a maximum value of the POC value, at a timing at which a picture 18 is generated. In this case, an IDR picture 18 is inserted next to the P picture 17, whereupon the POC value is reset. Though not depicted in FIG. 7, P pictures are successively inserted after the IDR picture 18, and the process described above is executed repetitively. It is to be noted that the maximum value of the POC value may be changed suitably. While it is indicated that the maximum value of the POC value is 1000 as an example in FIG. 7, the maximum value is not limited to this.
As related art documents, for example, Japanese Laid-Open Patent Publications Nos. 2013-243480, 2009-81898, 2008-154187 and 2009-290463, and US Patent Application Publications Nos. 2005/0031030, 2008/0152012 and 2009/0296809 are available.